Upload of photos using BMP extension

Hi,

Tested:

• using Dolphin demo site I've added allowed extension bmp for photos. Clearing cache.
• try to upload a bmp image to an event. This doesn't work on the demo site and on my own site not for other mods either.

Issues:

1. bmp extension doesn't work
2. there are no warning comment (little blue icon) next to the upload function which extensions work or not. So user isn't aware that he shouldn't even try a bmp.
3. there are no alert to the user after upload that the picture have failed due to not supported extension. The photo is just missing to the confusion of the user.